Enhanced thermoelectric performance of nanostructured topological insulator Bi_2Se_3

摘要

To enhance thermoelectric performance by utilizing topological properties of topological insulators has attracted increasing attention. Here, we show that as grain size decreases from microns to ～80nm in thickness, the electron mobility μ increases steeply from 12-15 cm~2 V~(-1) s~(-1) to ～600 cm~2 V~(-1) s~(-1), owing to the contribution of increased topologically protected conducting surfaces. Simultaneously, its lattice thermal conductivity is lowered by ～30%-50% due to enhanced phonon scattering from the increased grain boundaries. As a result, thermoelectric figure of merit, ZT, of all the fine-grained samples is improved. Specifically, a maximum value of ZT = ～0.63 is achieved for Bi_2Se_3 at T = ～570K.